Lubricants containing quaternary ammonium dithiocarbamates



United States Patent ABSTRACT OF THE DISCLOSURE Lubricant inhibited from oxidation by a minor portion of a monoor bis-(quaternary ammonium) dithiocarbamate in which the quaternary radical is substituted by hydrocarbyl radicals of up to 24 carbon atoms, and the sum of the carbon atoms in these radicals is greater than 8.

This invention relates to lubricants protected from oxidation by certain additives. More particularly, it relates to lubricant compositions stabilized with certain quaternary ammonium alkyldithiocarbamates. Most specifically, the invention is concerned with metal-soap containing greases inhibited by such compounds.

It is usually desirable to add to lubricant compositions certain compounds which function as antioxidants, retarding the buildup of corrosive end products of oxidation which eventually cause wear and failure of machine parts which are being lubricated. Of particular importance is the problem of retarding corrosion in parts lubricated with greases such as wheel bearings, etc. Metal dithiocarbamates, in particular zinc alkyldithiocarbamates, have been used extensively for oxidation inhibition of lubricants. However, in many uses, in particular in greases thickened with metallic soaps, the presence of heavy metal ions such as Zn++, Cu++, Fe+++, etc. appears to contribute to the lowering of bearing life. Therefore, it is particularly desirable to employ an antioxidant which is effective but lacks the harmful metallic ions of such material.

Attempts have been made to provide such a metal-free, dithiocarbamic acid-based antioxidant, but materials which have been used, chiefly amine salts, are volatile and are of uncertain stability after dissipating quickly from the protected lubricant, leaving it bare of protection from oxidation.

US. Patent No. 2,973,297 discloses as fungicidal materials certain quaternary ammonium salts of alkyldithiocarbamic and alkylbisdithiocarbamic acids. The materials may be applied to plants by dispersion in an emulsified oil, such as xylene. No disclosure is made of the antioxidant activity of the particular materials.

It has now been found that oleaginous lubricants elfectively inhibited from oxidation and rendered noncorrosive result when certain quaternary ammonium dithiocarbamates are added to the lubricant base. These antioxidant materials are of the following formula:

in which R R R and R are selected from the group consisting of alkyl, aryl, alkaryl and aralkyl radicals of not more than 24 carbon atoms and the sum of carbon atoms in R R R and R is greater than 8, and X and Y are selected from the group consisting of hydrogen, alkyl radicals of 1 to 6 carbon atoms and electronegative radicals of the formula:

in which R is selected from the group consisting of alkylene, arylene, alkarylene and aralkylene radicals of Substitution of a triamine and not more than 15 carbon atoms, n is 1 to 3 equal to the number of negative charges on the dithiocarbamate anion. Thus, the antioxidants can be described as quaternary ammonium salts of mono-, bisand trisdithiocarba-mates.

The quaternary ions of the additives of this invention are preferably derived from bases having greater than 8 carbon atoms, more preferably, from those having from about 12 to about 40 carbon atoms. An example of a preferred compound is a quaternary ion in which one of the substituent groups is an alkylbenzyl radical of 12 to 24 carbon atoms. A particularly useful quaternary ion is one containing an alkylbenzyl radical having about 12 alkyl carbon atoms.

The groups which are substituted on the nitrogen atom may contain further relatively inert substituents, such as hydroxyl, halogen, etc. A particularly desirable embodiment of the invention is a quaternary cation having a hydroxyethyl substituent group.

This dithiocarbamate ion, as noted before, is derived from a secondary amine, a primary diamine or a triamine having one secondary amino and two primary amino groups. Examples of suitable secondary monoamines are diethylamine, dipropylamine, ethylpropylamine, etc. Suitable primary diamines include ethylenediamine, propylenediamine, phenylenediamine, etc. Alkyl or alkylene amines are preferred in each of the cases.

The salts of this invention may be prepared by the reaction of a quaternary'ammonium salt, such as a chloride, with a suitable metal dithiocarbamate. They may also be prepared by the reaction of a quaternary ammonium hydroxide with an amine and carbon disulfide. The following equation illustrates the latter method used in preparing a monodithiocarbamate:

Likewise, bisdithiocarbamates can be prepared by reacting two molecules of the quaternary base, two molecules of carbon disulfide and one molecule of a diamine. changing to three mols each of the base and carbon disulfide will produce a trisdithioearbamate.

The preparation of many metal dithiocarbamates is described in The Dithiocarbamates and Related Compounds, Thorn/Ludwig, Elsevier Publishing Company, 1962.

The following examples illustrate the preparation of the compounds of this invention.

Example I.Preparation of alkyZbenzyldimethylhydroxyethylammoniwm ethylenebisdithiocarbamate 15.0 g. (0.25 mol) of ethylenediamine was stirred in a beaker at room temperature with 42.0 g. (0.55 mol) of carbon disulfide and 20 g. (0.50 mol) of sodium hydroxide. To this mixture was added 410 g. (0.50 mol) of alkylbenzyldimethylhydroxyammonium chloride. The mixture was stirred, and a heavy precipitate formed. The material was filtered, washed with water and dried in an oven. The yield was 138 g. of a dark oil containing 3.3% nitrogen (5.8% theory) and 9.8% sulfur (13% theory).

Example II.-Preparation of dioleyldimethylammonium ethylenebisa'ithiocarbamate 3.0 g. (0.05 mol) of ethylenediamine and g. of dioleyldimethylammonium hydroxide in water were stirred together in a beaker at room temperature. To this mixture, 7.6 g. (0.10 mol) of carbon disulfide was added with stirring. An exothermic reaction took place. The material was then heated for four hours at 200 F. on a hotplate to remove water. The yield was a dark oil having 3.9% nitrogen (4.3% theory).

3 Example III.--Preparatin of monoquatemary dithiocarbamate 100 g. (0.1 mol) of 50% dioleyldimethylammonium hydroxide in water and 10 g. (0.1 mol) of di-n-butyl- 4 hibitors in greases. The inhibitors were added to a lithium soap base grease. The grease samples were then subjected to an ASTM bomb oxidation test and a high speed bearing life test. The bomb oxidation test ASTM D-942-50 briefly involves subjecting a 20 g. sample of the grease amine were mixed in a beaker and cooled in an ice bath. 5 to an initial pressure of 110 p.s.i. of oxygen at 210 F. 6 H101) of Carbon disulfide Was added With Stirringfor one hundred hours and measuring the pressure loss The product yield after water separation was 60 g. of at the end of the period. A greater loss indicates greater viscous oil. oxidation of the grease sample.

Samples of a quaternary ammonium bisdithiocarbamate The bearing life test is known as the Navy High Speed and a zinc dithiocarbamate were subjected to a white oil 10 Bearing Test and is described in Federal Test Method oxidator test. In this test, the inhibitors to be tested are 331.1. In this test, a ball bearing was operated at 10,000 placed in a sample of the solventand acid-refined oil r.p.m. continuously for approximately twenty-two hours at a concentration of 10 millimoles/liter; the sample is at 300 F. The apparatus was then cooled to room temheated to 340 F., and oxygen is bubbled through the perature during a period of two hours. This procedure of solution until 1000 ml. of the oxygen is absorbed in 100 operating and cooling was repeated until there was bearg. of the oil. ing failure. Bearing Life is the number of hours to The following table shows results of these tests: bearing failure.

TABLE I Oxida- Cation Anton tion Time, hrs.

Base Oil Alone 0. 14

i M- 11a zn++ scN 12 (CH2)J-C H;

i t t It can be seen that the quaternary ammonium bisdithiocarbamates illustrated compare favorably under the ex- Table II shows the results of the above-mentioned tests. The base grease was bis-2-ethylhexyl sebacate thickened treme conditions of the oxidator test with the widely used with 15% by weight lithium stearate. The bearing life zinc dithiocarbamate oxidation inhibitor.

Of greater significance are the performances of the infor each sample and the geometric means (in parentheses) are given.

TABLE II Additive 9 Bomb Oxlda- High Speed Type l Cone, tion Pressure Bearing Lite l Percent Drop (p.s.i.) at 300 F., hr. Cation Anton g After Hrs.

1 at 210 F.

Base Grease Alone. n 27 53; 240; 380

s Butyl I i Zine Dithiocarbamatu Zn -SC-N 2 3.3 196; 76 (136) Butyl I Butyl i I DO Zn "1 'S-C-N 5 230; 265 (250) E Butyl i Butyl Quaternary (CIEH35)2(CH3)2N+ 'SCN 5 Dithiocarbamate. 460' 482 (470) Butyl Quaternary (C1aH:o)2(CHa) 2N S S l -1. 5 Bisdtthiocarbamate. II {I 2 -O. 0 420; 560 (480) -SC NC Hr-C H2NHCS' l S S Do R -N' -C HzC H2011 ll 1 1.0

-S-C -NC H:C HiNH--C -S- C H; C H3 l =-Cr2 alkyl i i These data show the remarkable eifectiveness of the quaternary dithiocarbamates in reducing oxidation and increasing stability in greases. Thus, at equal concentrations the inhibitors are from two to three times as efiective in increasing bearing life as the metallic dithiocarbamate. It may also be seen that the oxidation of the grease is inhibited to a much greater degree by the quaternary compounds.

The oleaginous lubricants which comprise the bases for the compositions of this invention are those oily or greasy materials most commonly employed in lubrication. Examples of these materials are natural and synthetic oils and greases made from these oils. Base materials which are not suitable for the compositions of this and are not classified as oleaginous lubricants are those inorganic substances sometimes used in lubricating functions, such as molybdenum disulfide, tungsten disulfide, graphite, ground glass, ground basalt, etc.

The oils which can be used as base oils for the compositions of this invention include a wide variety of lubricating oils, such as naphthenic-base, paraifin-base and mixed-base lubricating oils, other hydrocarbon lubricants, e.g., lubricating oils derived from coal products, and synthetic oils, e.g., alkylene polymers (such as polymers of propylene, butylene, etc., and the mixtures thereof), alkylene oxide-type polymers (e.g., alkylene oxide polymers prepared by polymerizing alkylene oxide, e.g., propylene oxide polymers, etc., in the presence of water or alcohols, e.g., ethyl alcohols), carboxylic acid esters (e.g., those which were prepared by esterifying such carboxylic acids as adipic acid, azelaic acid, suberic acid, sebacic acid, alkenylsuccinic acid, fuman'c acid, maleic acid, etc., with the alcohols, such as butyl alcohol, hexyl alcohol, 2-ethylhexyl alcohol, pentaerythritol, etc.), liquid esters of acids of phosphorus, alkylbenzenes, polyphenyls (e.g., biphenyls and terphenyls), alkylbiphenyl ethers, polymers of silicon (e.g., tetraethyl silicate, tetraisopropyl silicate, tetra(4-methyl-2-tetraethyl) silicate, hexyl(4-methyl-2-pentoxy) disiloxane, poly(methyl) siloxane, and poly(methylphenyl) siloxane, etc.

The base oils can be used individually or in combi nations, wherever miscible or wherever made so by use of mutual solvents.

In addition to the inhibitors described in this invention, the lubricating compositions of this invention may also contain other lubricating oil and grease additives, such as oiliness agents, extreme pressure agents, oxidation inhibitors, rust inhibitors, corrosion inhibitors, viscosity index improving agents, dyes, lubricating oil detergents, etc.

I claim:

1. A composition comprising a major portion of a lubricant and a minor amount sufiicient to inhibit oxida- 6 tion of a quaternary ammonium dithiocarbamate of the general formula:

in which R R R and R are selected from the group consisting of alkyl, aryl, alkaryl and aralkyl radicals of up to 24 carbon atoms and the sum of the carbon atoms in R R R and R is greater than 8, X and Y are selected from the group consisting of hydrogen, alkyl radicals of 1 to 6 carbon atoms and electronegative radicals of the formula:

in which R is selected from the group consisting of alkylene, arylene, alkarylene and aralkylene radicals of not more than 15 carbon atoms and n is 1 to 3 equal to the number of negative charges on the dithiocarbamate anion.

2. The composition of claim 1 in which the lubricant is an oil of lubricating viscosity.

3. The composition of claim 1 in which the lubricant is a grease.

4. The composition of claim 3 is which the lubricant is a lithium soap base grease.

5. The composition of claim 2 in which at least one of the groups represented by R R R and R is an. alkylbenzyl radical.

6. The composition of claim 5 in which R is alkylbenzyl, R and R are methyl, R is hydroxyethyl, R is ethylene, Y is hydrogen and n is 2.

7. The composition of claim 6 in which R and R are oleyl, R and R are methyl, R is ethylene, Y is hydrogen and n is 2.

8. The composition of claim 3 propyl-substituted benzyl.

in which R is tetra- References Cited UNITED STATES PATENTS 2,160,851 6/1939 Faust 252-336 2,400,106 5/1946 Denison et al. 25233.6 2,786,814 3/1957 McDermott 25233.6 2,805,996 9/1957 Deger 25233.6 2,973,297 2/1961 Bakkeren et al. 16738 3,151,076 9/1964 Epton et al 252-33.6 3,230,168 1/1966 Low 252-33.6

DANIEL E. WYMAN, Primary Examiner. I. VAUGHN, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,354,085 November 21, 1967 Bruce W. Hotten that error appears in the above numbered patread as It is hereby certified (1 that the said Letters Patent should ent requiring correction an corrected below.

for "emulsified""read' emulsifiable line 7 thereof,

Column 1, line 49,

for that portion columns '3 and 4, TABLE II, fourth column, column 6, lines 3 to 6,

for "1" read 2 of the formula reading \R read Signed and sealed this 17th day of December 1968.

(SEAL) Attest:

Edward M. Fletcher, Jr. EDWARD BRENNER Commissioner of Patents Attesting Officer 

1. A COMPOSITION COMPRISING A MAJOR PORTION OF A LUBRICANT AND A MINOR AMOUNT SUFFICIENT TO INHIBIT OXIDATION OF A QUATERNARY AMMONIUM DITHIOCARBAMATE OF THE GENERAL FORMULA: 